syscall(3) returns -1 and sets errno on error, unlike "syscall"
instruction.

Systems which have <= 32/64 CPUs are unaffected. Test won't bounce
to all CPUs before completing if there are more of them.

Fixes: 1f5bd0547654 ("proc: selftests: test /proc/uptime")
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

 tools/testing/selftests/proc/proc-uptime-002.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/tools/testing/selftests/proc/proc-uptime-002.c
+++ b/tools/testing/selftests/proc/proc-uptime-002.c
@@ -17,6 +17,7 @@
 // while shifting across CPUs.
 #undef NDEBUG
 #include <assert.h>
+#include <errno.h>
 #include <unistd.h>
 #include <sys/syscall.h>
 #include <stdlib.h>
@@ -54,7 +55,7 @@ int main(void)
 		len += sizeof(unsigned long);
 		free(m);
 		m = malloc(len);
-	} while (sys_sched_getaffinity(0, len, m) == -EINVAL);
+	} while (sys_sched_getaffinity(0, len, m) == -1 && errno == EINVAL);
 
 	fd = open("/proc/uptime", O_RDONLY);
 	assert(fd >= 0);